JER (EGJJ) airfield is in the south-west corner of the island, only about 3 - 4 nm from the north coast at St Mary.
It seems the incident started around 1900Z, when the wind at the airfield was southerly at about 30 kt, in moderate, occasionally heavy rain. Presumably there would have been turbulence and downdrafts over the cliffs on the north coast, plus layers of low stratus cloud.
EGJJ 032350Z 25030G41KT 9999 BKN014 14/12 Q0990 NOSIG
EGJJ 032320Z 25029KT 9999 BKN014 14/12 Q0990 NOSIG
EGJJ 032250Z 25033KT 9999 FEW010 BKN014 14/12 Q0991 NOSIG
EGJJ 032220Z 24026KT 7000 FEW010 BKN013 14/13 Q0991 NOSIG
EGJJ 032150Z 23029KT 9999 FEW010 BKN014 14/12 Q0992 NOSIG
EGJJ 032120Z 23026KT 9999 FEW008 BKN014 14/12 Q0992 NOSIG
EGJJ 032050Z 22029KT 9999 FEW008 SCT012 BKN018 13/12 Q0992 NOSIG
EGJJ 032020Z 20029KT 7000 -RA FEW005 BKN008 12/11 Q0993 TEMPO BKN012
EGJJ 031950Z 20028G39KT 5000 -RA SCT006 BKN009 11/10 Q0994 RERA TEMPO 9999 BKN012
EGJJ 031920Z 17029KT 3000 RA SCT006 BKN010 11/10 Q0995 TEMPO +RA BKN005
EGJJ 031850Z 17028KT 5000 RA SCT008 BKN010 10/09 Q0996 TEMPO 3000 +RA BKN005
EGJJ 031820Z 17024KT 7000 RA FEW008 BKN012 10/09 Q0998 TEMPO 4000 BKN006
EGJJ 031750Z 19019KT 8000 RA FEW010 BKN020 11/09 Q1000 BECMG 5000 BKN010
EGJJ 031720Z 18018KT 9999 -RA FEW012 SCT020 BKN040 11/09 Q1002 BECMG 5000 RA BKN010
EGJJ 031650Z 21017KT 9999 -RA FEW018 BKN045 11/08 Q1002 BECMG 5000 RA BKN012
EGJJ 031620Z 21022KT 9999 -RA SCT020 BKN035 11/08 Q1004 RERA BECMG 5000 RA BKN012
EGJJ 031550Z 21016G26KT 9999 -RA SCT025 BKN040 11/07 Q1004 BECMG 5000 RA BKN012
Link for current BBC News item, which also reports the fishermen have been rescued alive:
BBC News - Search-and-rescue plane crash lands on Jersey